Sanding mandrel



June 1959v w. b. WHITNEY SANDING MANDREL Filed Jan. 13, lss.

INVENTOR. WALTER D. WHITNEY ATTORNEYS United States Patent SANDING MANDREL Walter 1). Whitney, Mountainview, Calif. Application January 13, 1958 Serial No. 708,502

7 Claims. (Cl. 51190) This invention relates to a sanding mandrel for supporting a sleeve of abrasive material and has for one of its objects the provision of improved expandable means for retaining the sanding sleeve on the mandrel.

It is common practice in drnm sanders of the cylin drical or conical type having a rubber backing member over which a tubular sanding sleeve is fitted, to compress the backing member so as to radially expand it into tight engagement with the inner side of the sleeve. The sleeve is thereby held on the mandrel and rotates therewith for performing various power sanding tasks.

Generally, there are two primary difiiculties inherent in these prior art devices. In most sanding operations, as on automobile bodies and the like, it is desirable that the mandrel backing material retain its softness and resiliency so as to provide good even abrasion on the surface being sanded. In the case of the conventional mandrel compressing the backing material to retain the abrasive sleeve thereon hardens the former to an undesirable extent.

Not only is the backing material stifiened by compression but bulges and depressions are generally formed in its surface resulting in uneven sanding characteristics. This uneven surface of the conventional sanding mandrel may often cause the sanding sleeve to chatter on the work producing an undesirable result.

, It is therefore another object of this invention to provide a sanding mandrel which does not rely upon the compression of the backing material to securethe tubular abrasive sleeve in place. i

Another object of this invention is the provision of a sanding mandrel adapted to carry a sleeve of abrasive material which includes unique means at one end of the mandrel for securing the abrasive sleeve in place.

Still another object of this invention is the provision.

of a separate tightening member on drum type sanding mandrel which secures an abrasive sleeve on the backing member of said mandrel.

Other objects and advantages will become apparent from the following description taken in connection with the accompanying drawings in which:

Fig. l is a perspective view on a reduced scale of a rotary power tool with the sanding mandrel of this invention mounted therein;

Fig. 2 is a side elevational view of the sanding mandrel of this invention, partly broken away and in section to show internal details;

Fig. 3 is an exploded perspective view of the sanding mandrel of this invention; and,

Fig. 4 is a partial side elevational view of theend of a sanding mandrel of modified form from that shown' in Fig. 2.

In detail, the device of this invention is best illustrated. in its unassembled form in Fig. 3 in which it is seen to' comprise an elongated cylindrical base member 1 which is provided with a flange or head 2 at one end and abut- .figuration so long as it is circular in cross section and is provided with a central bore 7 for mounting coaxially on member 1. From a practical standpoint one end of memher 6 should be recessed, as shown at 8 in Fig. 2, to receive head 2 which serves to hold backing member 6 on base member 1. In the assembled view, Fig. 2, member 6is seen to extend from head 2 to shoulder 3 on base member 1. A centrally apertured washer 9, of a diameter slightly smaller than the largest end of base member 6, is received on the reduced diameter portion 4 of base member 1 and abuts against shoulder 3. It will be understood that the length of base member 6 is such that it may just come in contact with washer 9, but that shoulder 3 prevents washer 9 from exerting any compressive force on base member 6.

A compressible tightening member 10, in the form of a washer of resilient, rubber-like material, is provided with a;-central aperture 11 and is received on portion 4 of base member 1 adjacent the side of washer 9 opposite backing I member 6. The outside diameter of tightening member 10 is substantially similar to that of the large end of- Adjacent the other side of tightening member 10 a rigid, centrally apertured disc 12 is received on the reduced end portion 4 of base member 1. Disc 12 is likewise of a smaller diameter than tightening member 10 and said tightening member is interposed between said disc 12 and washer 9, for a purpose to be described.

Means for. connecting the sanding mandrel of this invention to a rotary power tool, illustrated at 13 in Fig. l, is provided in the form of-a cylindrical member 14 (Figs. 2, 3) having a threaded portion 15, adapted to be threadedly received in threaded bore 5 of base member 1, and an internally threaded bore 16 (Fig. 2) in its opposite end for connection to the spindle of the power tool 13.

Screwing connecting member 14 into base member 1 causes disc 12 to be urged toward washer 9 thereby axially compressing tightening member 10 and causing the same to expand radially. The hand of the threads on portion 15 and 5 of connecting member 14 and base member 1, respectively, are such that rotation of the sanding mandrel by the power tool 13 causes connecting member 14,to be tightened into base member 1. Likewise, the

threads 16 are also formed to tighten connecting member 14 on the spindle of the power tool during operation.

The sanding mandrel of this invention is adapted to carry a tubular sleeve 19 (Fig. 2) of abrasive material.

-Such'sleeves are made in a variety of sizes and grits and may be formed for a frusto-conical mandrel as shown, or a cylindrical mandrel. It is obvious that the device of this invention encompasses both such forms which may be generally referred to as drum sanders.

Backing member 6 and tightening member 10 are so formed that sleeve 19 maybe slipped over the end of member 6 and into snug fitting relationship with backing member 6. It will be noted from Fig. 2 that sleeve 19 extends beyond the inner end of backing member 6 and over tightening member 10. The sliding fit which sleeve 3 19 thus maintains with backing member 6 is not, however, sufiicient to hold the sleeve in place during sanding operations.

Hence the provision of tighteningmember 10 which,

upon screwing connecting member14 inwardly, is radia1= ly expanded into tight force-able engagement with the inner surface of the end of sleeve 19. Tightening member 10, in being squeezed between disc 12' and washer 9, expands radially into sufiicient frictional. engagement with the inner surface of sleeve 19 to .hold the sleeve in place during the sanding operations. In effect, tightening member 10 acts as a relatively short end section of the sleeve backing member which radially expanded without effecting the major portion of backing member '6. Backing member 6 thereby retains itsnatural resiliency and its smooth surface so as to provide a stable backing for the abrasive sleeve 19. The undesirable characteristics of previous devices of this type mentioned above are thereby overcome by the device of this invention.

A rubber washer 20 may be interposed between connectingmember 14 and disc 12 to resist any loosening OfcOnnecting member 14 with respect to disc 12. A set screw 21 (Fig. 2) may be provided in threaded bore 5 to limit the inner movement of threaded portion of member 14.

It will be noted, with reference to Fig. 2, that backing member 6 is maintained in its soft undisturbed condition throughout its length from washer 9 to its outer end at head 2, providing a supporting surface for sleeve 19 throughout the length of the latter. In the modification of Fig, 4, where it is desired to provide a sanding surface on the end of the mandrel, a cap 22 of resilient material is provided. Cap 22 is surfaced with the cover 23 of abrasive material and is provided with an axially extending threaded shank 24'which is received in a complementa ry threaded hole inthe end-of base member 1.

Cap 22 may thus be releasably secured to theend ofbase member 1 for providing an abrasiveend'portion on the sanding mandrel of this invention.

Although the invention has been described and illustrated in detail it is obvious that other modifications could be made therein without departing from the spirit and scope of the invention.

I claim:

1. A: sanding mandrel adapted to carry a sleeve of abrasive material for rotary sanding operations, comprissing: a resilient body of circular cross section adapted to be inserted into said abrasive sleeve for supporting the same, means for attaching said body to a rotary power source for rotating the same, a separate, deformable tightening member in continuationof said body and connected for rotation therewith, and means for radially expanding said member into tight forceable engagementwith the inner surface of said abrasive sleeve,

2; A sanding mandrel'adapted to carry a sleeve of abrasive material for rotary sanding operations, comprising: a resilient body of circular cross section adapted. to be inserted into said abrasive sleeve for supporting the same, means for attaching said body to a rotarypower source for rotating the same, a separate, deformabletightening member in continuation of said body and connected for rotation therewith, and means for radially expanding.

said member into tight forceable engagement with the inner surface of said abrasive sleeve, said last mentioned means including an opposed pair of abutment members on opposite sides of said tightening member movable. toward each other for axially compressing said, tightening member and thereby causing it to expand radially.

3. A sanding mandrel adapted to support a sleeveof abrasive material and to be driven by rotary power means, comprising: an elongated base member providedwith connecting means at one end for attachment to said power means, abutment means on said base member pro-- viding a face directed; toward. said one end, a soft, rubberabutment means and the other end of said base memberand adapted to receive said abrasive sleeve with a sliding fit over the outer surface thereof, a compressible tightening member having an outer surface in continuation of said backing member received on said base member adjacent said face and adapted to receive the end portion of said sleeve over the outer. surface thereof, and means for axially compressing said tightening member against said abutment means for radially expanding said tightening member into forceable engagement with the inner surface of said end portion of said sleeve.

4. A sanding device comprising an elongated base member provided witha. connection at one end for attachment to a rotary power tool, a resilient backing member of circular cross section received on said base member for rotation therewith about its axis, a tubular sanding sleeve of abrasive material received on said backing member for support'thereby and having one end extending past the end of said backing member at said one endof'said base membena compressible tightening member received on said base member within said one end of'said sleeve, and means for radially compressing said,

tightening member for axially expanding the same into frictional'holding engagement with saidone end of said sleeve.

5. A sanding device comprising an elongated basemember provided with a connection at one end for attachment to a rotary power tool, a resilient backing member of circular cross section received on said base member'for rotation therewith about its axis, a tubular sanding sleeve abrasive material and to be driven by rotary powermeans, comprising: an elongated base member provided with connecting means at one end'for'attacluncnt to said power means, abutment means on said base member providing a face directed toward said one end, a soft, rubberlike backing member of circular cross section mounted on said base member extending axially between said abutment means and the other end'of said base member and adapted to receive said abrasive sleeve with a sliding fit over, the outer surface thereof, a compressible tightening member having an outer surface in continuation of said backing member received on said base member adjacent said face and adapted to receive the end'portion of said sleeve over the outer surface thereof, and means for axially compressing said-tightening member against said abutment means for radiallyexpanding said tightening memberinto forceable engagement with the inner surface of said'end portion of said sleeve, said last mentioned meansincluding disc means abutting said tightening member ontheside oppositesaid abutment means and screw threadedly engaging a central bore in said base member for urging said disc means toward said abutment means.

7. A sanding mandrel adapted to support a sleeve of abrasive material and to be driven by rotary power means, comprising: an elongatde base member provided with connecting means at one end for attachment to said power means,- abutrnent-means on said base member providing a..face directed toward said one end, a soft, rubber-like backing:member of circularcross section mounted on saidzbasemember, extending axially between said abutment meansand the:other end of said .basemember and.

adaptedio receive said. abrasivesleevewith a sliding ,fit

ber on the side opposite said abutment means and screw threadedly engaging a central bore in said base member for urging said disc means toward said abutment means, and stop means for limiting the movement of said disc 5 means.

References Cited in the file of this patent UNITED STATES PATENTS Hapgood Sept. 9, 1873 Keavy May 1, 1888 

